|
| ABSORBERS | BARRIERS |
 |
 |
| Use:
To reduce noise reflection. To dissipate noise energy.
Physical Properties: Porous, fibrous and sometimes covered with protective membranes. Noise enters the absorber and is partly dissipated (absorbed) within the material. Some is transmitted. Some is reflected. Absorber performance is expressed as a decimal value. A perfect absorber is rated at 1.00. The higher the decimal value the more effective the absorber will be. Effectiveness is expressed as NRC (Noise Reduction NRC: Percentage of acoustical energy absorbed calculated as an average of laboratory test data at several frequencies. |
Use:
To block transmission of noise.
Physical Properties: Non-porous, high density and usually non-fibrous. Barriers are generally flexible or damped. The noise is blocked, reflected and re-routed in another direction. Barrier materials are tested and rated for their Sound Transmission Loss capability. The number is stated in dB and the higher number signifies the better barrier. Effectiveness is expressed as STC (Sound Transmission Class). STC: Single number rating derived from decibel loss data at several frequencies. |
Noise Reduction Coefficients of Materials |
NRC |
Sound Transmission Class of Materials |
STC |
| Brick, unglazed | .05 | 1 lb. density barrier material | 26 |
| Concrete block | .05 | 1 lb. density transparent curtain | 26 |
| 1/8” pile Carpet | .15 | 5/8” Gypsum wallboard | 30 |
| 5/16” pile Carpet and foam | .35 | 3/16” Steel wall | 31 |
| Concrete floor | .00 | 2” fiberglass curtain with 1 lb. barrier | 29 |
| Plaster, smooth finish | .05 | 2” thick metal panel (solid and perforated) | 35 |
| Plywood paneling, 1/4” thick | .10 | 4” thick metal panel (solid and perforated) | 41 |
| Water surface (as in swimming pool) | .00 | 12” thick concrete | 53 |
| 1” thick fiberglass curtain | .70 | 3/8” plasterboard | 26 |
| 3” thick HUSH WEDGE™ foam | .86 | 22 gauge steel | 25 |
| 4” thick smooth surface foam | .89 | Solid core wood door, closed | 27 |
| 4” thick metal panel | .95 | Concrete block wall, unpainted | 44 |
 |
Noise
and Vibration Control, Inc.
|
1-610-863-6300
|